The clinical and functional characteristics of the involutional phase of proliferative diabetic retinopathy shall be examined. From examination of patients referred to the Department of Ophthalmology for evaluation of complications of diabetic retinopathy, we will determine those who have spontaneously entered the involution phase and who are suitable for inclusion within this study. Clinical characteristics of end-stage retinopathy used to determine eligibility include stabilization of vision, optic nerve pallor, attenuatted arterioles and veins and replacement of neovascularization by glial tissue. Suitable eyes will not show evidence of extensive traction retinal detachment or prior photocoagulation treatment. The clinical characteristics will be documented by retinal photography and fluorescein angiography. The retinal function will then be studied. This will include visual field examination, dark adaptometry, electroretinography, electro-oculography and colour vision testing. After initially defining the clinical and functional characteristics of the involution phase, we will study the natural history by repetition of the testing procedures on an annual basis. Similar studies will be done on eyes with evidence of active proliferative retinopathy to obtain baseline control data to compare with that obtained from the involutional eyes.